After replaying the game numerous times, I have occasionally had one
or two testimonies show up with different dates than the ones
indicated, including two testimonies with the same date showing up
in two different locations. This is a glitch, but it's not important
as long as you are able to find all the testimonies. Unfortunately,
even after applying patch 1.2, I had a testimony not show up at all
(the one under the safe) and had to replay. I could understand that
if I'd tried to replay from a previous save, but I'd started a new
game.

So there may be issues even after patching the game. In general
though, the patch seems to have helped with the disappearing
inventory bug. Perhaps it would be helpful if, after you patch the
game, you go into the game's save location at
C:\Users\your-username\AppData\LocalLow\Microids\Subject13 and
manually delete all pre-patch saved games -- just to be sure all
previous unpatched save information (and mis-information) is gone.